A direct injection engine has adopted a configuration in which a fuel injection valve is mounted onto a mounting hole in a cylinder head (housing), and fuel is injected directly into a cylinder from a nozzle at the tip of this fuel injection valve. Accordingly, it is required to prevent leakage of combustion gas at high pressure from an annular clearance gap between the fuel injection valve and the mounting hole.
A structure in which an annular groove is provided on an outer peripheral surface of the fuel injection valve, and a rubber or resin seal ring is installed into the annular groove has been known as a sealing structure against the leakage (refer to patent documents 1 through 6). Moreover, a configuration in which two kinds of seal rings, rubber and resin, are combined has been proposed in a patent document 7, and a configuration in which a metal ring is arranged on the tip side of a rubber O-ring has been proposed in a patent document 8.
[Patent Document 1]: Japanese Laid-Open Patent Application Publication No. 2002-070696,
[Patent Document 2]: Japanese Laid-Open Patent Application Publication No. 2002-081548,
[Patent Document 3]: Japanese Laid-Open Patent Application Publication No. 2002-081549,
[Patent Document 4]: Japanese Laid-Open Patent Application Publication No. 2002-202030,
[Patent Document 5]: Japanese Laid-Open Patent Application Publication No. 2002-317733,
[Patent Document 6]: Japanese Laid-Open Patent Application Publication No. 2002-364494,
[Patent Document 7]: Japanese Laid-Open Patent Application Publication No. 11-013593, and
[Patent Document 8]: Japanese Laid-Open Patent Application Publication No. 2000-310332.